Comparison of electron beam computed tomography scanning and conventional risk factor assessment for the prediction of angiographic coronary artery disease

Coronary Artery Calcium Data and Reporting System (CAC-DRS): A Primer

The Coronary Artery Calcium Data and Reporting System (CAC-DRS) is a standardized reporting method for calcium scoring on computed tomography. CAC-DRS is applied on a per-patient basis and represents the total calcium score with the number of vessels involved. There are 4 risk categories ranging from CAC-DRS 0 to CAC-DRS 3. CAC-DRS also provides risk prediction and treatment recommendations for each category. The main strengths of CAC-DRS include a detailed and meaningful representation of CAC, improved communication between physicians, risk stratification, appropriate treatment recommendations, and uniform data collection, which provides a framework for education and research. The major limitations of CAC-DRS include a few missing components, an overly simple visual approach without any standard reference, and treatment recommendations lacking a basis in clinical trials. This consistent yet straightforward method has the potential to systemize CAC scoring in both gated and non-gated scans.

The coronary calcium score is a more accurate predictor of significant coronary stenosis than conventional risk factors in symptomatic patients: Euro-CCAD study

AIMS

In this retrospective study we assessed the predictive value of the coronary calcium score for significant (>50%) stenosis relative to conventional risk factors.

METHODS AND RESULTS

We investigated 5515 symptomatic patients from Denmark, France, Germany, Italy, Spain and the USA. All had risk factor assessment, computed tomographic coronary angiogram (CTCA) or conventional angiography and a CT scan for coronary artery calcium (CAC) scoring. 1539 (27.9%) patients had significant stenosis, 5.5% of whom had zero CAC. In 5074 patients, multiple binary regression showed the most important predictor of significant stenosis to be male gender (B=1.07) followed by diabetes mellitus (B=0.70) smoking, hypercholesterolaemia, hypertension, family history of CAD and age but not obesity. When the log transformed CAC score was included, it became the most powerful predictor (B=1.25), followed by male gender (B=0.48), diabetes, smoking, family history and age but hypercholesterolaemia and hypertension lost significance. The CAC score is a more accurate predictor of >50% stenosis than risk factors regardless of the means of assessment of stenosis. The sensitivity of risk factors, CAC score and the combination for prediction of >50% stenosis when measured by conventional angiogram was considerably higher than when assessed by CTCA but the specificity was considerably higher when assessed by CTCA. The accuracy of CTCA for predicting >50% stenosis using the CAC score alone was higher (AUC=0.85) than using a combination of the CAC score and risk factors with conventional angiography (AUC=0.81).

CONCLUSION

In symptomatic patients, the CAC score is a more accurate predictor of significant coronary stenosis than conventional risk factors.

Coronary artery calcium: 0.5 mm slice-thickness reconstruction with adjusted attenuation threshold outperforms 3.0 mm by validating against spatially registered intravascular ultrasound with radiofrequency backscatter

RATIONALE AND OBJECTIVES

Coronary artery calcium (CAC) images can be reconstructed with thinner slice thickness on some modern multidetector-row computed tomography scanners without additional radiation. We hypothesized that the isotropic 0.5-mm CAC reconstruction outperforms the conventional 3.0-mm reconstruction in detecting and quantifying coronary calcium, and we proposed to compare them by validating against spatially registered intravascular ultrasound with radiofrequency backscatter-virtual histology (IVUS-VH).

MATERIALS AND METHODS

Twenty-seven patients were enrolled, and 5976 mm of coronary arteries were analyzed. A semiautomatic software was developed to coregister CAC and IVUS-VH on a detailed slice-by-slice basis. Calcium detection and calcium volume quantification were evaluated and compared using varying calcium attenuation thresholds. Algorithms for deriving individualized optimal threshold and comparable Agatston score on the 0.5-mm reconstruction were developed.

RESULTS

The isotropic 0.5-mm reconstruction achieved significantly higher area under receiver-operating curve than the conventional 3.0-mm reconstruction (0.9 vs. 0.74, P < .001). Using the optimal threshold, the 0.5-mm reconstruction had higher sensitivity (0.79 vs. 0.65), specificity (0.85 vs. 0.77), positive predictive value (0.42 vs. 0.29), and negative predictive value (0.97 vs. 0.94) than the 3.0 mm. Individualized optimal threshold was significantly correlated with the image noise (r = 0.66, P < .001) in the 0.5-mm reconstruction.

CONCLUSIONS

By optimizing the calcium threshold, the 0.5-mm reconstruction is superior to the conventional 3.0-mm in detecting and quantifying calcium, which may improve the clinical value of CAC without additional radiation.

Incremental diagnostic value of epicardial adipose tissue for the detection of functionally relevant coronary artery disease

BACKGROUND AND AIM

To determine the incremental diagnostic value of epicardial adipose tissue (EAT) volume in addition to the coronary artery calcium (CAC) score for detecting hemodynamic significant coronary artery disease (CAD).

METHODS AND RESULTS

122 patients (mean age 61 ± 10 years, 61% male) without a previous cardiac history underwent a non-contrast CT scan for calcium scoring and EAT volume measurements. Subsequently all patients underwent invasive coronary angiography (ICA) in conjunction with fractional flow reserve (FFR) measurements. A stenosis >90% and/or a FFR ≤0.80 were considered significant. Mean EAT volume and CACscore were 128 ± 51 cm(3) and 418 ± 704, respectively. The correlation between EAT volume and the CACscore was poor (r = 0.11, p = 0.24). Male gender (odds ratio [OR] 2.86, p = 0.01), CACscore ([cut-off value 100] OR 3.31, p = 0.003, and EAT volume ([cut-off value 92 cm(3)] OR 4.28, p = 0.01) were associated with flow-limiting disease. The multivariate model revealed that only male gender (OR 2.50, p = 0.045), CAC score (OR 3.60, p = 0.005), and EAT volume (OR 4.95, p = 0.02) were independent predictors of myocardial ischemia. Using the cut-off values of 100 (CAC score) and 92 cm(3) (EAT volume), sensitivity, specificity, negative predictive value, positive predictive value, and accuracy for detecting functionally relevant CAD as indicated by FFR were 71, 57, 77, 50 and 63% and 91, 29, 85, 44 and 52% for the CACscore and EAT volume, respectively. Adding EAT volume to the CAC score and cardiovascular risk factors did not enhance diagnostic performance for the detection of significant CAD (p = 0.57).

CONCLUSION

EAT volume measurements have no diagnostic value beyond calcium scoring and cardiovascular risk factors in the detection of hemodynamic significant CAD.

Diagnostic efficacy of vessel specific coronary calcium score in detection of coronary artery stenosis

BACKGROUND

Coronary artery calcification which is determined quantitatively by coronary calcium scoring has been known as a sign of coronary stenosis and thus future cardiac events; hence it has been noticed on spotlight of researchers in recent years. Developing different method for early and optimal detection of coronary artery disease (CAD) is really essential as CAD are the first cause of death in population.

OBJECTIVES

To evaluate predictive value of vessel specific coronary artery calcium (CAC) score in predicting obstructive coronary artery disease.

PATIENTS AND METHODS

In this diagnostic test study we evaluated patients with coronary computed tomography angiography (CCTA) and CAC score which had been referred to two referral radiology center in Tehran, Iran and finally we selected 2525 patients in a single and sequential pattern to create a diagnostic study. The whole-heart CAC scores and vessel specific CAC scores were calculated individually for the 4 major epicardial coronary arteries in 2 distinct group; group A ( patients with previous history of CABG) and group B (patients without history of CABG). For evaluation of obstruction tree cut off points were described: 0 > ; at least 1 segment with any kind of stenosis, ≥ 50; at least 1 segment with stenosis ≥ 50, ≥ 70; at least 1 segment with stenosis ≥ 70.

RESULTS

Mean of coronary calcium scores in terms of each coronary artery vessel increase by increasing coronary stenosis grade in group B; LAD, RCA, LCX respectively have mean CAC score 6.06, 6.21 and 5.04 in normal patients and 221.6, 226.7 and 106.6 in patients with complete stenosis. As expected these findings don't work for group A. Also By increasing calcium score cutoff in all four vessels sensitivity decreased and specificity increased but steal LAD had higher sensitivity than other vessels and LM had higher specificity. Thus using calcium score method is useful for ruling out stenosis in LAD while calcium score of LM can predict existence of stenosis in LM. However none of the vessel specific CAC can reach to 100% sensitivity and specificity of CCTA method.

CONCLUSIONS

CCTA is highly superior than vessel specific CAC score thus to minimize patients radiation does maybe we can eliminate CAC scan as a routinely perform procedure at the beginning of the CCTA.

Metabolically-healthy obesity and coronary artery calcification

OBJECTIVES

The purpose of this study was to compare the coronary artery calcium (CAC) scores of metabolically-healthy obese (MHO) and metabolically healthy normal-weight individuals in a large sample of apparently healthy men and women.

BACKGROUND

The risk of cardiovascular disease among obese individuals without obesity-related metabolic abnormalities, referred to as MHO, is controversial.

METHODS

We conducted a cross-sectional study of 14,828 metabolically-healthy adults with no known cardiovascular disease who underwent a health checkup examination that included estimation of CAC scores by cardiac tomography. Being metabolically healthy was defined as not having any metabolic syndrome component and having a homeostasis model assessment of insulin resistance <2.5.

RESULTS

MHO individuals had a higher prevalence of coronary calcification than normal weight subjects. In multivariable-adjusted models, the CAC score ratio comparing MHO with normal-weight participants was 2.26 (95% confidence interval: 1.48 to 3.43). In mediation analyses, further adjustment for metabolic risk factors markedly attenuated this association, which was no longer statistically significant (CAC score ratio 1.24; 95% confidence interval: 0.79 to 1.96). These associations did not differ by clinically-relevant subgroups.

CONCLUSIONS

MHO participants had a higher prevalence of subclinical coronary atherosclerosis than metabolically-healthy normal-weight participants, which supports the idea that MHO is not a harmless condition. This association, however, was mediated by metabolic risk factors at levels below those considered abnormal, which suggests that the label of metabolically healthy for obese subjects may be an artifact of the cutoff levels used in the definition of metabolic health.

Coronary artery calcium score: a review

Context

Coronary artery disease (CAD) is the foremost cause of death in many countries and hence, its early diagnosis is usually concerned as a major healthcare priority. Coronary artery calcium scoring (CACS) using either electron beam computed tomography (EBCT) or multislice computed tomography (MSCT) has been applied for more than 20 years to provide an early CAD diagnosis in clinical routine practice. Moreover, its association with other body organs has been a matter of vast research.

Evidence Acquisition

In this review article, techniques of CACS using EBCT and MSCT scanners as well as clinical and research indications of CACS are searched from PubMed, ISI Web of Science, Google Scholar and Scopus databases in a time period between late 1970s through July 2013 and following appropriate selection, dealt with. Moreover, the previous and ongoing research subjects and their results are discussed.

Results

The CACS is vastly applied in early detection of CAD and in many other research fields.

Conclusions

CACS has remarkably changed the screening techniques to detect CAD earlier than before and is generally accepted as a standard of reference for determination of risk of further cardiac events.

Different value of coronary calcium score to predict obstructive coronary artery disease in patients with and without moderate chronic kidney disease

PURPOSE

The coronary calcium score (CCS) predicts significant coronary artery disease (CAD) in the general population. While moderate chronic kidney disease (CKD) is associated with high CCS, the use of CCS to predict significant CAD in these patients is unknown.

METHODS

A total of 704 patients underwent computed tomography coronary angiography for the assessment of CCS and CAD. Sixty-nine (10 %) patients had moderate CKD, defined by an estimated glomerular filtration rate (eGFR) between 30 and 59 mL/min/1.73m(2), and the remaining patients were considered to be without significant CKD (eGFR ≥ 60 mL/min/1.73m(2)).

RESULTS

Patients with moderate CKD were older, had a higher CCS, and a higher prevalence of obstructive CAD than patients without significant CKD. Receiver-operator curve analysis showed that CCS predicted the presence of obstructive CAD in both patients with moderate CKD and those without significant CKD. In patients with moderate CKD, the optimal cut-off value of CCS to diagnose obstructive CAD was 140 (sensitivity 73 % and specificity of 70 %), and is 2.8 fold higher than in patients without significant CKD (cut-off value = 50; sensitivity 75 % and specificity 75 %).

CONCLUSION

The present results demonstrate that CCS can predict obstructive CAD in patients with moderate CKD, although the optimal cut-off value is higher than in patients without significant CKD.

Coronary artery calcium scoring on different 64-detector scanners using a low-tube voltage (80 kVp)

PURPOSE

The aim of this study was to compare the calcium score and reproducibility of coronary artery calcium scores obtained on the four kinds of 64-detector computed tomography (CT) scanners using standard (120 kVp) and low tube voltage (80 kVp) scan techniques.

MATERIALS AND METHODS

We scanned 80 and 120 kVp on all scanners. We calculated Agatston, volume, and mass scores for coronary artery calcium scoring on each scanner and compared the coefficients of variation of the calcium scores to evaluate reproducibility of among CT scanners.

RESULTS

The averages of the total mean Agatston score, total mean volume score, and total mean mass score at 80 kVp/120 kVp were 798.9/683.8, and 627.2/567.3, and 157.1/156.7, respectively. The total mean mass score was almost constant irrespective of the tube voltage. The total mean coefficients of variation for the four CT scanners were lower at 80 than 120 kVp (4.1% vs. 10.2% [total mean Agatston score], 3.2% vs. 9.6% [total mean volume score], and 3.2% vs. 9.4% [total mean mass score]).

CONCLUSION

Use of the low tube voltage technique can reduce variations in the coronary artery calcium scores obtained on different CT scanners.

Utility of coronary artery calcium scoring in the evaluation of patients with chest pain

Although coronary artery calcium (CAC) scoring has an established role in risk-stratifying asymptomatic patients at intermediate risk of coronary heart disease (CHD), its utility in the evaluation of patients with chest pain is uncertain. We conducted a literature review of articles investigating the utility of: (1) CAC scoring in elective patients with indeterminate chest pain symptoms, (2) CAC as a "gatekeeper" in the triage of patients presenting to the emergency department (ED) with chest pain, and (3) the cost-effectiveness of the use of CAC scoring in the ED. We also evaluated the predictive accuracy of the absence of CAC in a pooled analysis of applicable studies. Only studies evaluating patients classified as low or intermediate risk were included. Low to intermediate risk was established by Framingham risk scores, Thrombolysis in Myocardial Infarction scores, Diamond-Forrester classification, or by the absence of typical angina symptoms, ischemic electrocardiogram, positive cardiac biomarkers, or a prior history of CHD. In our pooled analysis, the presence of any CAC resulted in a high sensitivity (range 70%-100%) for predicting the presence of obstructive coronary disease among symptomatic patients subsequently referred for coronary angiography. More importantly, a CAC score of 0 in low- and intermediate-risk ED populations with chest pain had a high negative predictive value (99.4%) for CHD events over an average follow-up of 21 months. CAC scoring also seems cost-effective in this population. Although further research is needed, carefully selected ED patients with a normal electrocardiogram, normal cardiac biomarkers, and CAC = 0 may be considered for early discharge without further testing.

The relationship between coronary artery calcification and myocardial perfusion in asymptomatic women

BACKGROUND AND OBJECTIVES

No data are available in Saudi Arabia on the relationship between coronary artery calcification (CAC) and myocardial perfusion scintigraphy (MPS) in asymptomatic women, for determining subclinical coronary artery disease (CAD). The main objective of this study was to investigate the relationship between the presence of CAC and stress-induced myocardial ischemia by MPS in asymptomatic women.

DESIGN AND SETTING

Single-center retrospective study over a 2-year period.

METHODS

One hundred and one women (mean [SD] age, 56 [11] years) without known CAD underwent both MPS and CAC scanning within 3 months. The frequency of ischemia by MPS was compared with the presence or absence of CAC and the number of CAD risk factors.

RESULTS

The prevalence of ischemic MPS was 22% (22/101). Among the 22 patients with ischemic MPS, the CAC score was 0 in 5 patients of 22 (23%), 1 to 200 in 4 patients of 22 (18%), and more than 200 in 13 patients of 22 (59%) (P=.0001). In contrast, among the 79 patients with normal MPS, the CAC score was 0 in 44 of 79 (56%) patients, 1 to 200 in 25 of 79 (32%), and more than 200 in 10 of 79 (13%). The presence or absence of CAC was the single most important predictor of the MPS result (P=.0001).

CONCLUSIONS

Moderate to severe CAC is associated with ischemic MPS in more than 50% of asymptomatic women with 2 or more CAD risk factors. Abnormal MPS is rarely associated with a 0 CAC score. Normal MPS does not exclude subclinical CAD. Therefore, CAC screening is an appropriate initial screening test for CAD in asymptomatic women.

Coronary CT and the coronary calcium score, the future of ED risk stratification?

Accurate and efficient evaluation of acute chest pain remains clinically challenging because traditional diagnostic modalities have many limitations. Recent improvement in non-invasive imaging technologies could potentially improve both diagnostic efficiency and clinical outcomes of patients with acute chest pain while reducing unnecessary hospitalizations. However, there is still controversy regarding much of the evidence for these technologies. This article reviews the role of coronary artery calcium score and the coronary computed tomography in the assessment of individual coronary risk and their usefulness in the emergency department in facilitating appropriate disposition decisions. The evidence base and clinical applications for both techniques are also described, together with cost- effectiveness and radiation exposure considerations.

Quantitative relationship between coronary artery calcium score and hyperemic myocardial blood flow as assessed by hybrid 15O-water PET/CT imaging in patients evaluated for coronary artery disease

BACKGROUND

The incremental value of CAC over traditional risk factors to predict coronary vasodilator dysfunction and inherent myocardial blood flow (MBF) impairment is only scarcely documented (MBF). The aim of this study was therefore to evaluate the relationship between CAC content, hyperemic MBF, and coronary flow reserve (CFR) in patients undergoing hybrid (15)O-water PET/CT imaging.

METHODS

We evaluated 173 (mean age 56 ± 10, 78 men) patients with a low to intermediate likelihood for coronary artery disease (CAD), without a documented history of CAD, undergoing vasodilator stress (15)O-water PET/CT and CAC scoring. Obstructive coronary artery disease was excluded by means of invasive (n = 44) or CT-based coronary angiography (n = 129).

RESULTS

91 of 173 patients (52%) had a CAC score of zero. Of those with CAC, the CAC score was 0.1-99.9, 100-399.9, and ≥400 in 31%, 12%, and 5% of patients, respectively. Global CAC score showed significant inverse correlation with hyperemic MBF (r = -0.32, P < .001). With increasing CAC score, there was a decline in hyperemic MBF on a per-patient basis [3.70, 3.30, 2.68, and 2.53 mL · min(-1) · g(-1), with total CAC score of 0, 0.1-99.9, 100-399.9, and ≥400, respectively (P < .001)]. CFR showed a stepwise decline with increasing levels of CAC (3.70, 3.32, 2.94, and 2.93, P < .05). Multivariate analysis, including age, BMI, and CAD risk factors, revealed that only age, male gender, BMI, and hypercholesterolemia were associated with reduced stress perfusion. Furthermore, only diabetes and age were independently associated with CFR.

CONCLUSION

In patients without significant obstructive CAD, a greater CAC burden is associated with a decreased hyperemic MBF and CFR. However, this association disappeared after adjustment for traditional CAD risk factors. These results suggest that CAC does not add incremental value regarding hyperemic MBF and CFR over established CAD risk factors in patients without obstructive CAD.

Coronary CT angiography: current status and continuing challenges

Coronary CT angiography has been increasingly used in the diagnosis of coronary artery disease owing to rapid technological developments, which are reflected in the improved spatial and temporal resolution of the images. High diagnostic accuracy has been achieved with multislice CT scanners (64 slice and higher), and in selected patients coronary CT angiography is regarded as a reliable alternative to invasive coronary angiography. With high-quality coronary CT imaging increasingly being performed, patients can benefit from an imaging modality that provides a rapid and accurate diagnosis while avoiding an invasive procedure. Despite the tremendous contributions of coronary CT angiography to cardiac imaging, study results reported in the literature should be interpreted with caution as there are some limitations existing within the study design or related to patient risk factors. In addition, some attention must be given to the potential health risks associated with the ionising radiation received during cardiac CT examinations. Radiation dose associated with coronary CT angiography has raised serious concerns in the literature, as the risk of developing malignancy is not negligible. Various dose-saving strategies have been implemented, with some of the strategies resulting in significant dose reduction. The aim of this review is to present an overview of the role of coronary CT angiography on cardiac imaging, with focus on coronary artery disease in terms of the diagnostic and prognostic value of coronary CT angiography. Various approaches for dose reduction commonly recommended in the literature are discussed. Limitations of coronary CT angiography are identified. Finally, future directions and challenges with the use of coronary CT angiography are highlighted.

Coronary artery calcium scoring and its impact on the clinical practice in the era of multidetector CT

With the suggestion of coronary artery calcium as an indicator of coronary artery disease 30 years ago, intense and controversial discussion regarding coronary artery calcium has been ongoing. Diverse techniques for evaluation of coronary artery calcium were suggested and validation of its feasibility has been followed up. Following establishment of reference standards, coronary artery calcium became widely utilized in clinical practice and scientific research. Originally coronary artery calcium scoring techniques were developed for prediction of cardiovascular risk. Additionally, coronary artery calcium scoring has been utilized as an indicator for other medical events. Recently, coronary artery calcium scoring used to be applied as a reference standard during scientific research. In this article, the topic of coronary artery calcium, from its introduction to its current usefulness, was discussed from the viewpoints of coronary artery calcium scoring techniques, imaging modalities, validation of the techniques, clinical feasibility of coronary artery calcium scoring beyond traditional cardiovascular risk prediction, and utilization of coronary artery calcium scoring as a reference standard. Popular coronary calcium scoring techniques comprises of Agatston, volume, and mass scores. Through validation of these techniques, pros and cons of each technique were analyzed and proper utility could be suggested. In parallel, the reference standards for Agatston and volume scores were established by age, sex, and race. Through the vigorous controversies, nowadays, the clinical feasibility of coronary artery calcium score as a surrogate marker of cardiovascular risk was acknowledged in the literature.

Cardiac risk stratification: role of the coronary calcium score

Coronary artery calcium (CAC) is an integral part of atherosclerotic coronary heart disease (CHD). CHD is the leading cause of death in industrialized nations and there is a constant effort to develop preventative strategies. The emphasis is on risk stratification and primary risk prevention in asymptomatic patients to decrease cardiovascular mortality and morbidity. The Framingham Risk Score predicts CHD events only moderately well where family history is not included as a risk factor. There has been an exploration for new tests for better risk stratification and risk factor modification. While the Framingham Risk Score, European Systematic Coronary Risk Evaluation Project, and European Prospective Cardiovascular Munster study remain excellent tools for risk factor modification, the CAC score may have additional benefit in risk assessment. There have been several studies supporting the role of CAC score for prediction of myocardial infarction and cardiovascular mortality. It has been shown to have great scope in risk stratification of asymptomatic patients in the emergency room. Additionally, it may help in assessment of progression or regression of coronary artery disease. Furthermore, the CAC score may help differentiate ischemic from nonischemic cardiomyopathy.

Incremental value of the CT coronary calcium score for the prediction of coronary artery disease

Objectives:

To validate published prediction models for the presence of obstructive coronary artery disease (CAD) in patients with new onset stable typical or atypical angina pectoris and to assess the incremental value of the CT coronary calcium score (CTCS).

Methods:

We searched the literature for clinical prediction rules for the diagnosis of obstructive CAD, defined as ≥50% stenosis in at least one vessel on conventional coronary angiography. Significant variables were re-analysed in our dataset of 254 patients with logistic regression. CTCS was subsequently included in the models. The area under the receiver operating characteristic curve (AUC) was calculated to assess diagnostic performance.

Results:

Re-analysing the variables used by Diamond & Forrester yielded an AUC of 0.798, which increased to 0.890 by adding CTCS. For Pryor, Morise 1994, Morise 1997 and Shaw the AUC increased from 0.838 to 0.901, 0.831 to 0.899, 0.840 to 0.898 and 0.833 to 0.899. CTCS significantly improved model performance in each model.

Conclusions:

Validation demonstrated good diagnostic performance across all models. CTCS improves the prediction of the presence of obstructive CAD, independent of clinical predictors, and should be considered in its diagnostic work-up.

Relationship between baseline coronary calcium score and demonstration of coronary artery stenoses during follow-up MESA (Multi-Ethnic Study of Atherosclerosis)

OBJECTIVES

The MESA (Multi-Ethnic Study of Atherosclerosis) is a population-based study of 6,814 men and women. We sought to analyze the relationship between the extent of coronary artery calcium (CAC) at baseline and the severity of coronary stenoses in clinically indicated coronary angiography studies during follow-up.

BACKGROUND

CAC is an established predictor of major cardiovascular events. Yet, the relationship between CAC and the distribution and severity of coronary artery stenoses has not been widely explored.

METHODS

All MESA participants underwent noncontrast enhanced cardiac computed tomography during enrollment to determine baseline CAC. We analyzed 175 consecutive angiography reports from participants who underwent coronary catheterization for clinical indications during a median follow-up period of 18 months. The relationship between baseline CAC and the severity of coronary stenosis detected in coronary angiographies was determined.

RESULTS

Baseline Agatston score was 0 in only 7 of 175 (4%) MESA participants who underwent invasive angiography during follow-up. When coronary arteries were studied separately, 13% to 18% of coronary arteries with >or=75% stenosis had 0 calcium mass scores at baseline. There was close association between baseline calcium mass score and the severity of stenosis in each of the coronary arteries (test for trend, p < 0.001). For example, mean calcium mass scores for <50%, 50% to 74%, and >or=75% stenosis in the left anterior descending coronary artery were 105.1 mg, 157.2 mg, and 302.2 mg, respectively (p < 0.001). Finally, there was a direct relationship between the total Agatston Score at baseline and the number of diseased vessels (test for trend, p < 0.001).

CONCLUSIONS

The majority of patients with clinically indicated coronary angiography during follow-up had detectable coronary calcification at baseline. Although there is a significant relationship between the extent of calcification and mean degree of stenosis in individual coronary vessels, 16% of the coronary arteries with significant stenoses had no calcification at baseline.

Assessment of subclinical atherosclerosis and cardiovascular risk

Conventional cardiac risk factors do not fully explain the incidence of coronary artery disease and coronary events. Risk stratification and therapy based solely on these conventional risk factors may exclude a population who would otherwise benefit from lifestyle and risk factor modification. Recent efforts to improve our ability to recognize individuals and populations at increased risk of coronary events have focused on the noninvasive imaging of atherosclerosis, both in coronary and extracoronary arterial beds, or the identification of "non-traditional" serum markers. We review the complimentary role of these newer methods of risk stratification in the context of conventional risk factor evaluation.

The role of coronary artery calcification score in clinical practice

Background

Coronary artery calcification (CAC) measured by electron-beam computed tomography (EBCT) has been well studied in the prediction of coronary artery disease (CAD). We sought to evaluate the impact of the CAC score in the diagnostic process immediately after its introduction in a large tertiary referral centre.

Methods

598 patients with no history of CAD who underwent EBCT for evaluation of CAD were retrospectively included into the study. Ischemia detection test results (exercise stress test, single photon emission computed tomography or ST segment analysis on 24 hours ECG detection), as well as the results of coronary angiography (CAG) were collected.

Results

The mean age of the patients was 55 ± 11 years (57% male). Patients were divided according to CAC scores; group A < 10, B 10 – 99, C 100 – 399 and D ≥ 400 (304, 135, 89 and 70 patients respectively). Ischemia detection tests were performed in 531 (89%) patients; negative ischemia results were found in 362 patients (183 in group A, 87 in B, 58 in C, 34 in D). Eighty-eight percent of the patients in group D underwent CAG despite negative ischemia test results, against 6% in group A, 16% in group B and 29% in group C. A positive ischemia test was found in 74 patients (25 in group A, 17 in B, 16 in C, 16 in D). In group D 88% (N = 14) of the patients with a positive ischemia test were referred for CAG, whereas 38 – 47% in group A-C.

Conclusion

Our study showed that patients with a high CAC score are more often referred for CAG. The CAC scores can be used as an aid in daily cardiology practice to determine further decision making.

The impact of the menopause on coronary artery calcification examined by multislice computed tomography scanning

BACKGROUND AND AIMS

To examine whether there is a difference in coronary artery calcification (CAC) scores between males and females aged above 50 years.

METHODS AND RESULTS

A total of 479 subjects aged between 40 and 70 years with no clinical or family history of cardiovascular disease (CVD) were enrolled for this study. All subjects were assessed by multislice CT scanning (MCTS), and the CAC scores obtained were assigned to one of four quartiles for further assessment and comparison. The main outcome evaluated was the percentage of high CAC scores and mean CAC scores, comparing males and females of different age groups. This study found that the percentage of high CAC scores increased markedly from 5% (40-49 age group) to 21.2% (50-59 age group) among females. The increase was significantly less when comparing males from different age groups (from 25% in the 40-49 age group to 31.2% in the 50-59 age group). Females had higher odds ratios (ORs) postmenopausally (4.3 in the 50-59 age group) than males in the same age group (1.6).

CONCLUSIONS

These initial findings seem to indicate that above 50 years of age, CAC is more dependent on age in females than in males, which might be due to the effect of the menopause.

Absolute coronary artery calcium scores are superior to MESA percentile rank in predicting obstructive coronary artery disease

BACKGROUND

Coronary artery calcium scoring (CAC) is an excellent non-invasive method to evaluate coronary atherosclerotic burden. To better predict the risk of future events in an individual, their absolute CAC score is compared to an age- and gender-matched cohort in order to assign a percentile rank. However, it is unknown whether absolute CAC or percentile rank is better in predicting obstructive coronary artery disease (CAD). We hypothesized that absolute CAC is superior to percentile rank in predicting obstructive CAD.

METHODS

210 consecutive patients referred to our institution for CAC and coronary artery computed tomography angiography (CTA) were included. CAC scores were expressed as Agatston score; percentile rank as published by the Multi-Ethnic Study of Atherosclerosis. Coronary artery stenoses were graded semi-quantitatively. Receiver operating characteristics curves (ROC) were used to assess the performance of CAC to predict obstructive CAD.

RESULTS

In the overall group, the area under the curve (AUC) was significantly greater for absolute CAC compared to MESA percentile rank in predicting obstructive CAD (0.80 vs. 0.72, P = 0.006). Subgroup analysis revealed similar findings: AUC for absolute CAC was greater than for MESA percentile rank in males (0.82 vs. 0.71, P = 0.008), females (0.78 vs. 0.72, P = 0.085), symptomatic patients (0.78 vs. 0.72, P = 0.067) and in asymptomatic subjects (0.89 vs. 0.74, P = 0.05).

CONCLUSION

Absolute CAC is superior to MESA percentile rank in predicting obstructive CAD. This finding was seen in both symptomatic and asymptomatic patients as well as in males and females.

Therapeutic Implications of Coronary Artery Calcium Using Cardiac Computed Tomography

The objective of this document is to review the clinical applicability of coronary artery calcium (CAC) scoring in both asymptomatic and symptomatic patients at risk for cardiovascular disease. We begin by describing the pathological basis of atherosclerosis, the characteristic stages of atherosclerotic plaque development, and the mechanism and role of arterial calcification in advanced atherosclerotic lesions. We also explain the utility of CAC scoring in cardiovascular risk assessment, discuss the most current clinical methods for measuring CAC, and examine major clinical studies reporting CAC scores in both asymptomatic and symptomatic heart patients. Lastly, the current recommendations for CAC scoring as stated by the American College of Cardiology/American Heart Association (ACC/AHA) are outlined, and a number of considerations for future research are provided. Atherosclerosis begins when certain factors cause chronic endothelial injury, which eventually leads to the build up of fibrofatty plaques in the intima of arterial blood vessels. In time, blood vessel walls can weaken, thrombi can form and plaques can send emboli to distal sites. There are six characteristic stages of plaque development. Mature plaques may be calcified in an active process comparable to bone remodeling, where calcium phosphate crystals coalesce among lipid particles inside arterial walls. Calcification is only present in atherosclerotic arteries, and the site and levels of calcium are non-linearly and positively associated with luminal narrowing of coronary vessels. Calcification is also postulated to stabilize vulnerable plaques in atherosclerotic vessels. Recent studies have shown that CAC scoring can improve the management of both asymptomatic and symptomatic heart patients. Electron beam computed tomography (EBCT) and Multidetector computed tomography (MDCT) are two fast cardiac CT methods used to measure CAC. No matter what technique one uses, CAC is scored with either the Agatston or the “volume” score system. The ACC/ AHA currently finds it is reasonable for asymptomatic patients with intermediate Framingham risk scores (FRS) to undergo CAC assessment because these patients can be re-stratified into the high risk category if their CAC scores are ≥400. Conversely, CAC measurement in asymptomatic patients with low or high FRS is not warranted. There is also no evidence to suggest that high risk asymptomatic patients with no detectable coronary calcium should not be treated with secondary prevention medical therapy. For symptomatic patients, the ACC/AHA recommends CAC assessment as a second line technique to diagnose obstructive CAD, or when primary testing modalities are not possible or are unclear. Furthermore, they do not recommend the use of CAC measurement to determine the etiology of cardiomyopathy, to help identify patients with acute MI in the emergency room, or to assess the progression or regression of coronary atherosclerosis. Future research needs to incorporate calcium scores with percentile rankings, larger population samples, more women with at least intermediate Framingham risk, sufficient numbers of non-Caucasians, reports on cost-effectiveness, and data on populations with Chronic Kidney Disease, End Stage Renal Disease and Diabetes.

Combining myocardial perfusion imaging with computed tomography for diagnosis of coronary artery disease

PURPOSE OF REVIEW

To illustrate where the integration of computed tomography with myocardial perfusion single photon tomography may improve current diagnostic imaging paradigms and allow for enhanced risk stratification.

RECENT FINDINGS

Computed tomography has the advantage of detecting coronary atherosclerosis at its earliest stages and also identifying patients at high risk for having underlying myocardial ischemia, allowing initiation of appropriate therapeutic measures well before development of obstructive coronary artery disease. Single photon computed tomography can, conversely, clarify the anatomic findings of computed tomography, based on a functional assessment of myocardial blood flow, thereby guiding antiischemic and interventional therapies.

SUMMARY

Hybrid imaging with single photon tomography and computed tomography angiography may prove important from a diagnostic and therapeutic viewpoint in several clinical scenarios. It is likely that fusion imaging may more precisely tailor therapy, reduce healthcare costs and improve patient outcome over the next decade.

Impact of obesity on coronary artery calcification examined by electron beam computed tomographic scan

AIM

Obesity is highly associated with cardiovascular disease (CVD). The early and non-invasive diagnosis method for asymptomatic obese is desirable. The aim of this study was to examine the impact of obesity on coronary artery calcification (CAC) by electron beam computed tomographic (EBCT) scan.

METHODS

A total of 465 subjects (i) aged between 40 and 65 years, (ii) being Chinese, (iii) without clinical or historical angiographic obstruction or arrhythmia and (iv) without family history of CVD were enrolled in this study. All the subjects were assigned to one of the EBCT CAC score categories according to the quartiles: quartile 1 (<25%), quartile 2 (25-49%), quartile 3 (50-75%) and quartile 4 (>75%), for further assessment and comparison. The main outcome evaluated is the difference in CAC scores between obese [body mass index (BMI): > or =30 kg/m(2)] and healthy (BMI: 18.5-25.0 g/m(2)) BMI groups. The trends of the characteristics in CAC quartile groups and the odds ratios (ORs) were also evaluated.

RESULTS

The mean of CAC scores between the obese and the healthy BMI groups showed significant difference (p = 0.05). The obese subjects had higher ORs (1.0-5.8 times) than those with BMI < 23 kg/m(2), and male had higher ORs (1.1-3.6 times) than female, to develop the high CAC score quartile group.

CONCLUSION

This study demonstrated that the obese BMI group has a higher mean of CAC scores than the healthy BMI group of middle-aged, asymptomatic, Chinese adults. The obese males have higher risk of developing high CAC scores, which might induce CVD.

Presence and severity of noncalcified coronary plaque on 64-slice computed tomographic coronary angiography in patients with zero and low coronary artery calcium

How well absence of coronary artery calcium (CAC) predicts the absence of noncalcified coronary artery plaque (NCAP) has not been elucidated. We conducted a cross-sectional study of 554 outpatients to quantify NCAP prevalence as a function of CAC score. All patients underwent CAC scoring followed by 64-slice computed tomographic coronary angiography. Patients were categorized as having 0 CAC (416 patients) or low CAC (138 patients; men with CAC scores from 1 to 50 and women with scores from 1 to 10). Prevalence of detectable NCAP was 6.5% in patients with 0 CAC and 65.2% in those with low CAC. Compared with patients with 0 CAC, those with low CAC had markedly increased rates of NCAP occluding <50% of the arterial lumen (56.5% vs 6.0%, p <0.001) and > or =50% of the arterial lumen (8.7% vs 0.5%, p <0.001). In conclusion, in outpatients with a low to intermediate risk presentation and no known coronary artery disease, absence of CAC predicts low prevalence of any NCAP and very low prevalence of significantly occlusive NCAP. Low but detectable CAC scores are significantly less reliable in predicting plaque burden due to their association with high overall NCAP prevalence and nearly a 10% rate of significantly occlusive NCAP.

Hybrid SPECT-CT: Integration of CT coronary artery calcium scoring and angiography with myocardial perfusion

A natural extension of current imaging paradigms for diagnosing coronary artery disease may well be the integration of CT with myocardial perfusion single-photon CT (SPECT). Although there is a wealth of clinical information regarding the utility of SPECT, the value of CT in the cardiology arena has only recently been explored. CT has the advantage of detecting coronary atherosclerosis at its earliest stages, allowing initiation of appropriate therapeutic measures well before development of obstructive coronary artery disease. However, SPECT can clarify the anatomic findings of CT based on a functional assessment of myocardial blood flow, thereby guiding management decisions. Hybrid imaging with SPECT and CT angiography may prove important from a diagnostic and therapeutic view point in several clinical scenarios, and it is likely that over the next decade fusion imaging may more precisely tailor therapy, reduce healthcare costs, and improve patient outcome.

Evaluation of automated attenuation-based tube current adaptation for coronary calcium scoring in MDCT in a cohort of 262 patients

The aim of our study was to evaluate attenuation-based tube current adaptation in coronary calcium scoring using ECG-gated multi-detector-row CT (MDCT). A total of 262 patients underwent non-enhanced cardiac MDCT. Group 1 was scanned using a standard protocol with 120 kV and 150 mAs(eff). Groups 2-4 were scanned using an attenuation-based dose-adaptation template (CARE Dose) with different effective reference mAs settings (150, 180, 210 mAs(eff)). Body-mass index (BMI) and CT-dose index values were calculated for each patient. Image noise and subjective image quality were assessed. Regression analysis was performed, and the variation coefficient of image noise was determined. Compared to the standard scan protocol a dose reduction of 31.1% for group 2 and 20.1% for group 3 was observed. Measurement variation of image noise was smaller for the attenuation-based dose adaptation protocols (group 2-4) (16.2-17.1%) compared to the standard scan protocol (32.3%). Regression analysis of groups 2-4 showed better correlation with improved dose usage based on BMI (all P <or= 0.001). Median image quality was "excellent" in groups 2-4 and "good" in group 1. Automated attenuation-based tube current adaptation in coronary calcium scoring is technically feasible, can decrease patient dose, and reduces variation in image noise as a sign of improved dose usage.

High blood pressure in pregnancy and coronary calcification

A considerable proportion of pregnant women develop high blood pressure in pregnancy. Although it is assumed that this condition subsides after pregnancy, many of these women develop the metabolic syndrome later in life and are at increased risk to develop coronary heart disease. Atherosclerosis development is considered in between risk factors and occurrence of vascular symptoms. We set out to cross-sectionally study the relation of high blood pressure during pregnancy with risk of coronary calcification. The study population was composed 491 healthy postmenopausal women selected from a population-based cohort study. Information on high blood pressure during pregnancy was obtained using a questionnaire. Between 2004 and 2005, the women underwent a multidetector computed tomography (Philips Mx 8000 IDT 16) to assess coronary calcium. The Agatston score, volume, and mass measurements were used to quantify coronary calcium. A total of 30.7% of the women reported to have had high blood pressure in pregnancy. Body mass index (odds ratio [OR]: 1.05; 95% CI: 1.01 to 1.09) and diastolic blood pressure (OR: 1.03; 95% CI: 1.01 to 1.05) were significantly related to a history of high blood pressure in pregnancy. Age was significantly related to increased coronary calcification. Women with a history of high blood pressure during pregnancy had a 57% increased risk of having coronary calcification compared with those women without this condition (OR: 1.57; 95% CI: 1.04 to 2.37). After adjusting for age, the relation did not change (OR: 1.64; 95% CI: 1.07 to 2.53). We concluded that high blood pressure during pregnancy is associated with an increased risk of coronary calcification later in life.

Coronary Artery Calcium Scoring With Multislice Computed Tomography

OBJECTIVES

We sought to compare an 80-kVp coronary calcium scoring protocol with the standard protocol of 120 kVp in terms of accuracy and reproducibility and to assess its dose reduction potential.

MATERIALS AND METHOD

An anthropomorphic heart phantom with calcium cylinders was scanned with different tube currents at 80 kVp and 120 kVp using a 16-slice multislice CT (MSCT) scanner. An adapted threshold for 80 kVp was calculated. Accuracy and reproducibility for calcium mass, volume, and Agatston score were analyzed using F-tests. The radiation doses needed to produce artifact-free images were determined.

RESULTS

Accuracy (measurement errors: mass 120 kVp +4.6%, mass 80 kVp -6.9%, volume 120 kVp +78.8%, volume 80 kVp +58.2%) and reproducibility (F-tests: mass: P = 0.4998, volume: P = 0.9168, Agatston: P = 0.5422) were comparable at both tube voltages. Avoiding the appearance of artificial lesions, a CTDI(w,eff) of 10.7 mGy was needed at 120 kVp versus 4.6 mGy at 80 kVp (dose reduction of 57%).

CONCLUSIONS

Using an 80-kVp protocol in coronary calcium scoring, a relevant dose reduction is possible without compromising reproducibility and accuracy.

The accuracy of 1- and 3-mm slices in coronary calcium scoring using multi-slice CT in vitro and in vivo

The accuracy of coronary calcium scoring using 16-row MSCT comparing 1- and 3-mm slices was assessed. A thorax phantom with calcium cylinder inserts was scanned applying a non-enhanced retrospectively ECG-gated examination protocol: collimation 12 x 0.75 mm; 120 kV; 133 mAs(eff). Thirty-eight patients were examined using the same scan protocol. Image reconstruction was performed with an effective slice thickness of 3 and 1 mm. The volume score, calcium mass and Agatston score were determined. Image noise was measured in both studies. The volume score and calcium mass varied less than the Agatston score. The overall measured calcium mass compared to the actual calcium mass revealed a relative difference of +2.0% for 1-mm slices and -1.2% for 3-mm slices. Due to increased image noise in thinner slices in the patient study (26.1 HU), overall calcium scoring with a scoring threshold of 130 HU was not feasible. Interlesion comparison showed significantly higher scoring results for thinner slices (all P<0.001). A similar accuracy comparing calcium scoring results of 1- and 3-mm slices was shown in the phantom study; therefore, the potentially necessary increase of the patient's dose in order to achieve assessable 1-mm slices with an acceptable image-to-noise-ratio appears not to be justified.

Angina pectoris: evaluation in the office

Angina pectoris is a clinical manifestation of myocardial ischemia. Complete evaluation consists of a review of risk factors, a careful history, and, typically, a provocative test. Stress testing can be performed with exercise(treadmill, bicycle, or arm ergometry) or pharmacologic agents that increase cardiac work (dobutamine) or dilate the coronary vessels (adenosine or dipyridamole). Patients who have high-risk features found by clinical history or by stress testing should be referred for coronary angiography and possible revascularization. Comprehensive management of patients who have angina (with or without revascularization) includes smoking cessation,diet and weight control, vasculoprotective drugs (aspirin, statins, and possibly ACE inhibitors), and antianginal medications (nitrates, D-blockers, and calcium channel blockers). These strategies have led to an important reduction in morbidity and mortality over the past 2 decades, and the focus on implementing guidelines for patients who are currently undertreated is expected to improve outcomes further.

Coronary calcium scoring using 16-row multislice computed tomography: nonenhanced versus contrast-enhanced studies in vitro and in vivo

OBJECTIVES

We sought to assess the agreement of coronary artery calcium score in nonenhanced and contrast-enhanced multislice-spiral computed tomography.

MATERIALS AND METHODS

Vessel phantoms and 36 patients underwent nonenhanced and contrast-enhanced cardiac multislice-spiral computed tomography (Sensation 16; Siemens, Germany). Reconstruction-parameters: slice thickness 3 mm, increment 2 mm, kernels B35f and B30f. The Agatston score, calcium mass, and number of lesions were calculated. Images were scored using detection thresholds of 130 Hounsfield units (HU) and 350 HU. Based on the Agatston score, risk stratification was performed.

RESULTS

In the phantom and patient study, altering the threshold from 130 to 350 HU led to a significant decrease in the mean Agatston score (phantom: 54.6%, patients: 66.7%) and calcium mass (33.0%, 47.0%) (B35f). Contrast-enhanced studies (threshold: 350 HU) showed an increase of the mean Agatston score (71.0%, 20.7%) and calcium mass (81.0%, 16.0%) when compared with nonenhanced scans (threshold: 350 HU). A total of 57% of all patients were assigned to different risk groups.

CONCLUSIONS

Contrast material may simulate calcification; therefore, calculation of the coronary calcium score from contrast-enhanced images is not reliable.

Relationship between bone mineral density and myocardial infarction in US adults

Cardiovascular disease and osteoporosis have several common risk factors, and quite a few studies suggest a relationship between them. The objective of the present study was to explore the relationship between cardiovascular disease risk factors and bone mineral density in association with having had a previous myocardial infarction in a general population. This cross-sectional study was conducted using data for 5,050 women and men aged 50-79 years who participated in the Third National Health and Nutrition Examination Survey (NHANES III). Race/ethnic and gender-specific mean BMD values for young adults were used to determine race/ethnic and gender-specific T-scores to define osteoporosis and low BMD. Multiple logistic regression analysis revealed that subjects self-reporting a previous myocardial infarction had significantly higher odds (odds ratio 1.28, [95% confidence interval (CI), 1.01 to 1.63] p=0.04) of having low bone mineral density, when adjusting for cardiovascular disease and osteoporosis risk factors. Self-reported myocardial infarction was not significantly associated with low bone mineral density in women, (odds ratio 1.22, [95% CI, 0.80 to 1.86] p=0.37), but was significant in men, (odds ratio 1.39, [95% CI, 1.03 to 1.87] p=0.03). These findings demonstrate that male survivors of myocardial infarction have low bone mineral density. The pathophysiologic connection between the atherosclerotic and the osteoporotic processes needs further elucidation. It is also of importance to study the processes in both men and women.